The prevalence of HIV among injection drug users in cities where the use of black tar heroin is common is lower than the prevalence among IDUs in cities where the white powder form of heroin is prevalent, according to a study conducted by University of California-San Francisco researchers and published in a recent issue of the journal Substance Use & Misuse, UCSF Today reports. Researchers compared Drug Enforcement Administration data on the predominant types of heroin used in 20 U.S. cities between 1990 and 1993. White powder heroin is more common in East Coast cities, while black tar heroin is used more often in cities west of the Mississippi River. Researchers then compared that data with estimates of HIV prevalence during the same time frame among injection drug users and gay men in the same cities. Based on ethnographic, clinical, epidemiological and laboratory data, the researchers found several reasons why the risk of HIV transmission is lower among IDUs who use black tar heroin versus the powder form. Black tar heroin -- which is a "dark, gummy, resinous substance" -- must be heated to 165 degrees, which is sufficient to kill HIV, before it is injected, according to UCSF Today. In addition, injecting black tar heroin can cause venous sclerosis, which is a hardening of the veins and can lead to the loss of veins for injection sites. Therefore, black tar heroin users are likely to move quickly from intravenous injection to either subcutaneous or intramuscular injections, which previous studies have demonstrated are less efficient for HIV transmission. Black tar heroin also clogs syringes, leading IDUs to frequently rinse or dispose of their syringes. The rinsing of syringes could reduce the residual amount of blood and HIV left in them after injecting, according to the study.

Implications
Philippe Bourgois, a study co-author and chair of the UCSF Department of Anthropology, History and Social Medicine, said, "In California, injectors are constantly complaining that their needles clog. They almost always rinse their syringes immediately after shooting up in order to keep them from jamming. The grounds of shooting encampments and the walls of shooting galleries are wet from the water that they squirt through their used needles. This is not the case in New York, where white powder heroin does not 'gum up' needles." Dr. Daniel Ciccarone, assistant professor in the UCSF Departments of Family and Community Medicine and Anthropology, History and Social Medicine and lead author of the study, said, "In the early 1990s, about 40% of IDUs in New York City were HIV-infected, while only about 4% of IDUs in Los Angeles were infected with HIV. Yet in both cities, about 25% of gay men were HIV-infected. The solution to this discrepancy is found in the distribution and use of black tar heroin and is due to its unique chemical properties." Ciccarone added, "This data is valuable to public health authorities. Consider that if powder heroin were to become more widely available on the West Coast, public health agencies would need to prepare for the possibility that currently successful interventions to prevent HIV transmission among IDUs may lose much of their effectiveness" (Sheehy, UCSF Today, 1/27).

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